There have been known a feed containing Chlorella algae (green algae) for improving the red body color of prawn (refer to Japanese Patent Laid-Open No. 131894/1974), a feed additive comprising Spirulina algae (blue-green algae) (refer to Japanese Patent Publication No. 10017/1981) and a feed composition for prawn comprising Dunaliella algae (green algae) as the active component. These products have been used in order to improve the body color of prawn.